Nonvolatile memories are commonly either rewriteable devices, such as charge-storage devices, or one-time programmable devices, such as antifuse devices. Charge storage devices are usually programmed using Fowler-Nordheim tunneling or channel hot electron injection, while programming of antifuse devices requires applying the large voltage required to blow an antifuse. These programming mechanisms are slow and do not become faster as memories shrink, meaning that, as a rule, nonvolatile memories are slower to access than volatile memories. Monolithic three dimensional memories like the ones described in Johnson et al., U.S. Pat. No. 6,034,882, Knall et al., U.S. Pat. No. 6,420,215; and Lee et al., U.S. patent application Ser. No. 09/927,648, filed Aug. 13, 2001, because of the extra distance data must travel to reach upper levels of memory, are slower still.
There is a need, therefore, to improve the access time of nonvolatile memories.